FORMATION OF TUBES. 315 



attached to the inner surface of the corolla ; sometimes 

 these petaloid tubes replace the stamens, while at other 



Pig. 168. Corolla of Primula sinensis turned back to show a tubular 

 petal springing from it. One only is shown for the sake of clearness ; 

 they are generally numerous. 



times they appear to have no relation to those organs. 

 In the particular flowers now alluded to the tubular 

 form seems due to a dilatation, and not to a cohesion 

 of the margins. (See Cohesion, p. 23.) These tubular 

 petals resemble in form and colour almost precisely the 

 normal corolla in miniature, but are not surrounded by 

 a calyx, nor do they contain stamens, while the less 

 perfect forms show clearly their origin- from a single 

 tube -like organ. 



The formation of spurs or spur-like tubes in a quasi- 

 regular manner has been spoken of under the head of 

 Irregular Peloria, p. 228, but we occasionally meet 

 with tubular processes which seem to occur in an 

 irregular manner, and to have no reference to the 

 symmetrical plan of the flower, and which are due pro- 

 bably to the same causes as those which induce hyper- 

 trophy. Such spurs have frequently been seen on the 

 corolla of Digitalis purpurea, Antirrhinum majns^ 

 TuUpa Gesneriana, and occasionally on the sepals of 



' Chavannes, ' Mon. Antiri'h.' 



